The Egg Nebula (CRL 2688)

About this image

About this image
This is a thirty-second exposure taken
on the night of September 22nd 1994 (UT of observation 23/09/94:05:42).
This photograph shows a region 50 arc seconds square. The first
image has been compressed in brightness and very carefully windowed to
try to show the amazing structure in this object. With some image
viewers on certain computers, you may need to lighten the picture to
see everything that's there.
The second image is a pseudo-color version of the same original,
in a different attempt to reveal its oddities.
Observing conditions were not as good as the telescope optics, so that
this image has a "seeing" measurement
(average FWHM of several stars)
of about 0.9 arc seconds.
Orientation: N up with W to the left.

About this object
CRL 2688, also known as the Egg Nebula, is believed to be a proto-planetary
nebula, representing the transition to the comparatively well-studied
planetary nebula phase. It is well established that the progenitors of
planetary nebulae are stars at the tip of the asymptotic giant branch that
are losing mass in a `super-wind' phase. However, only a few objects are
known which can be reliably identified with this transition from star to
planetary, which makes their study very important. This optical image
shows the double-lobed nebula, which is illuminated by the central F5 star
which is hidden from our direct view by a dust torus. This torus appears
as a strong, though small, infrared source with a temperature of 150K.
The optical emission is very strongly polarized, at about 40%, which is
sufficient to be seen by eye with a Polaroid filter and a moderate-sized
telescope. The distance to CRL 2688 is uncertain, but is probably about
3000 light-years.